Semiconductor device and method for manufacturing the same

ABSTRACT

A semiconductor device and a method for manufacturing the same are disclosed. A recess gate structure is formed between an overlapping region between a gate and a source/drain so as to suppress increase in gate induced drain leakage (GIDL), and a gate insulation film is more thickly deposited in a region having weak GIDL, thereby reducing GIDL and thus improving refresh characteristics due to leakage current.

CROSS-REFERENCE TO RELATED APPLICATION

The priority of Korean patent application No. 10-2010-0089441 filed onSep. 13, 2010, the disclosure of which is hereby incorporated in itsentirety by reference, is claimed.

BACKGROUND OF THE INVENTION

Embodiments of the present invention relate to a semiconductor deviceand a method for manufacturing the same.

In general, semiconductor memories, which store information such as dataor commands of programs, include a DRAM and a SRAM. A DRAM is a memoryin which stored data may be read and other information may be stored.The DRAM allows information to be read therefrom and written thereon,but information stored in the DRAM is lost unless the information isperiodically rewritten within a designated period while power issupplied. Although a DRAM needs to be refreshed in this way, it has alow price per memory cell and a high integration density, and is thuswidely used as a high capacity memory.

A metal-oxide semiconductor field effect transistor (hereinafter,referred to as a “MOSFET”) is mainly used in memories, such as a DRAM,or logics. A MOSFET has a structure in which, after a gate oxide film, apolysilicon film, a gate metal, and a gate hard mask layer are depositedon a semiconductor substrate, gates are stacked thereon by amask/etching process to form channels.

If the size of a semiconductor device having a general structure isreduced, channel length is also shortened. When the channel length ofthe device is shortened, a short channel effect and gate induced drainleakage (GIDL) can occur. In order to prevent such deterioration, it isnecessary to increase gate channel length. However, increasing gatechannel length causes problems, such as increasing gate resistance anddeterioration of GIDL at a region where a gate and a source/drain regionoverlap with each other.

BRIEF SUMMARY OF THE INVENTION

Various embodiments of the present invention are directed to providing asemiconductor device and a method for manufacturing the same thatsubstantially obviate one or more problems due to limitations anddisadvantages of the related art.

An embodiment of the present invention relates to a semiconductor deviceand a method for manufacturing the same, in which a recess gatestructure is formed in a region where a gate and a source/drain overlapso as to suppress an increase in gate induced drain leakage (GIDL), anda gate insulation film is more thickly deposited in a region having weakGIDL, resulting in reduction of GIDL, thus improving refreshcharacteristics due to leakage current.

In accordance with an aspect of the present invention, a method formanufacturing a semiconductor device includes forming first recessesover a semiconductor substrate, forming a first insulation film over thefirst recesses and the semiconductor substrate, forming second recessesby etching the first insulation film and the semiconductor substrate,forming a second insulation film over the second recesses and the firstinsulation film, forming gate patterns over the second insulation filmat positions perpendicularly overlapping with the second recesses, andforming a second insulation film pattern and a first insulation filmpattern at both edges of the lower part of each of the gate patterns byetching the second and first insulation films until the semiconductorsubstrate is exposed, wherein the thicknesses of the second and firstinsulation film patterns are asymmetrical to each other.

The first recesses may be formed to have a depth of 100 Å˜400 Å.

The first insulation film may include an oxide film and may be formed tohave a thickness of 10 Å˜100 Å.

The second recesses may be formed to have a depth of 1200 Å˜1500 Å.

The second insulation film may include an oxide film and may be formedto have a thickness of 1 Å˜100 Å.

The width of the first recesses may be greater than the width of thesecond recesses.

The semiconductor substrate, connected to a storage node contact plugbetween the gate patterns, may have a step difference higher than thesemiconductor substrate connected to a bit line contact plug.

The forming of the gate patterns may include sequentially forming apolysilicon film, a metal silicide and an oxide film over the secondinsulation film, and etching the polysilicon film, the metal silicideand the oxide film using a gate pattern as a mask until the secondinsulation film is exposed.

The method may further include, after the forming of the gate patterns,forming third and fourth insulation films over the gate patterns, andetching the third and fourth insulation films until the semiconductorsubstrate is exposed.

In accordance with another aspect of the present invention, asemiconductor device includes gate patterns formed over a semiconductorsubstrate provided with recesses, and insulation film patterns formed atboth edges of the lower part of each of the gate patterns, wherein thethicknesses of the insulation film patterns formed at both edges of thelower part of each of the gate patterns are asymmetrical to each other.

The thickness of the insulation film pattern, which is formed over thesemiconductor substrate and connected to a storage node contact plugbetween the gate patterns, may be greater than the thickness of theinsulation film pattern, which is formed over the semiconductorsubstrate and connected to a bit line contact plug.

The semiconductor substrate connected to the storage node contact plugbetween the gate patterns may have a step difference higher than thesemiconductor substrate connected to the bit line contact plug.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating a semiconductor device according toan embodiment of the present invention.

FIGS. 2A to 2N are cross-sectional views illustrating a semiconductordevice and a method for manufacturing the same according to anembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. Asemiconductor device and a method for manufacturing the same accordingto embodiments of the present invention will hereinafter be describedwith reference to the appended drawings.

FIG. 1 is a plan view illustrating a semiconductor device and a methodfor manufacturing the same according to an embodiment of presentinvention.

Referring to FIG. 1, an active region 105 and recess gate patterns 200are formed over a semiconductor substrate.

In accordance with one embodiment, as shown in FIG. 1, the active region105 is formed to have a width of 205 nm in the horizontal direction andthe recess gate patterns 200 are formed to have a width of 35 nm in thehorizontal direction. Here, first recesses are formed to have a width of119 nm, and a width indicating the sum of the widths of the recess gatepatterns 200 and the width between the recess gate patterns 200 is 115nm. The width of first recesses is 4 nm larger than the sum of thewidths of the recess gate patterns 200 and the width of the spacebetween the recess gate patterns 200. Due to such a width difference, agate insulation film between the recess gate pattern 200 and asource/drain region may be thickly deposited during a subsequent gateinsulation film deposition process.

FIGS. 2A to 2N are cross-sectional views illustrating a semiconductordevice and the method for manufacturing the same according to thepresent invention.

Referring to FIG. 2A, after a photoresist film is formed over thesemiconductor substrate 100, a photoresist pattern 110 is formed throughan exposure and development process using a first recess mask. Thesemiconductor substrate 100 is etched using the photoresist pattern 110as an etching mask, thereby forming the first recesses 115. In anembodiment, the first recesses 115, formed by etching the semiconductorsubstrate 100, preferably have a depth of 100 Å˜400 Å, and mostpreferably have a depth of 200 Å˜300 Å.

Referring to FIG. 2B, after the photoresist pattern 110 is removed, afirst insulation film 120 is formed over the first recesses 115 and thesemiconductor substrate 100. In an embodiment, the first insulation film120 preferably includes an oxide film and has a thickness of 10 Å˜100 Å.The first insulation film 120 most preferably has a thickness of 20 Å˜40Å. Further, dry oxidation is preferably used to form the firstinsulation film 120.

Referring to FIGS. 2C and 2D, after a photoresist film is formed overthe first insulation film 120, a photoresist pattern 130 is formedthrough an exposure and development process using a recess gate mask.The first insulation film 120 and the semiconductor substrate 100 areetched using the photoresist pattern 130 as an etching mask, therebyforming second recesses 140. In an embodiment, the second recesses 140,formed by etching the first insulation film 120 and the semiconductorsubstrate 100, preferably have a depth of 1200 Å˜1500 Å, and mostpreferably have a depth of 1300 Å˜1400 Å.

Referring to FIGS. 2E and 2F, after the photoresist pattern 130 isremoved, a second insulation film 150 is formed over the second recesses140 and the first insulation film 120. In an embodiment, the secondinsulation film 150 preferably includes an oxide film and has athickness of 10 Å˜100 Å. The second insulation film 150 most preferablyhas a thickness of 50 Å˜60 Å. Further, dry oxidation is preferably usedto form the second insulation film 150. The total thickness of the firstand second insulation films 120 and 150 is greater than the thickness ofthe second insulation film 150 formed over the second recesses 140, thuspreventing current leakage between gates, which will be formed insubsequent processes.

Referring to FIGS. 2G and 2H, a polysilicon film 160 is formed over thesecond insulation film 150. In an embodiment, after the polysilicon film160 is formed, planarization and etching is performed, preferably usinga chemical mechanical polishing (CMP) method.

Referring to FIGS. 21 and 23, a metal silicide 170 and an oxide film 180are sequentially formed over the polysilicon film 160. After aphotoresist film is formed over the oxide film 180, a photoresistpattern 190 is formed through an exposure and development process usinga mask for gate pattern formation.

Referring to FIG. 2K, the oxide film 180, the metal silicide 170, andthe polysilicon film 160 are sequentially etched using the photoresistpattern 190 as an etching mask until the second insulation film 150 isexposed, thereby forming gate patterns 200, each of which consists of anoxide film pattern 185, a metal silicide pattern 175 and a polysiliconfilm pattern 165. In an embodiment, the gate patterns 200 are preferablyformed over the insulation film 150.

Referring to FIG. 2L, a third insulation film 210 is formed over thegate patterns 200 and the second insulation film 150. Preferably, thethird insulation film 210 includes an oxide film and performs abuffering function between the gate patterns 200 and other insulationfilms that will be formed during subsequent processes. In an embodiment,the third insulation film 210 preferably has a thickness of 10 Å˜50 Å,and most preferably has a thickness of 10 Å˜20 Å. Thereafter, an etchback process is performed on the third insulation film 210, etching thethird insulation film 210 so that it is formed in a liner pattern alongthe sidewalls and upper surfaces of the gate patterns 200.

Thereafter, a fourth insulation film 220 is formed over the thirdinsulation film 210 and the second insulation film 150. In anembodiment, the fourth insulation film 220 may include an oxide film ora nitride film. Preferably, the fourth insulation film 220 serves toprotect the sidewalls of the gate patterns 200 during a subsequentsource/drain formation process. In an embodiment, the fourth insulationfilm 220 preferably has a thickness of 10 Å˜100 Å, and most preferablyhas a thickness of 60 Å˜70 Å.

Referring to FIGS. 2M and 2N, anisotropic etching of the fourthinsulation film 220 is carried out until the third insulation film 210on the upper surfaces of the gate patterns 200 is exposed, therebyforming a fourth insulation film pattern 225 only over the sidewalls ofthe gate patterns 200 on which the third insulation film 210 isdeposited. Thereafter, an etch back process is performed on the secondand first insulation films 150 and 120, thereby exposing thesemiconductor substrate 100 and forming insulation film patterns A and Bover the sidewalls of the gate patterns 200. Impurities are injectedinto the exposed semiconductor substrate 100 through ion implantation230, thus forming source/drain regions (not shown). Here, thethicknesses of the insulation film patterns A and B are asymmetrical toeach other. The thickness of the insulation film pattern A is formed tobe greater than the thickness of the insulation film pattern B through apattern formation process to reduce gate induced drain leakage (GIDL)and to improve refresh characteristics due to leakage current. There isa step difference between the semiconductor substrate 100 provided withthe insulation film pattern B and the semiconductor substrate 100provided with the insulation film pattern A such that the semiconductorsubstrate 100 provided with the insulation film pattern B has a heightthat is lower than the semiconductor substrate 100 provided with theinsulation film pattern

A. As a result, a semiconductor device according to an embodiment of thepresent invention has a shorter channel length, thus reducing gateresistance.

As is apparent from the above description, in a semiconductor device anda method for manufacturing the same according to the present invention,a gate insulation film is more thickly deposited in a region (A) thathas relatively higher potential of GIDL, thereby reducing GIDL andimproving refresh characteristics due to leakage current.

The above embodiments of the present invention are illustrative and notlimitative. Various alternatives and equivalents are possible. Theinvention is not limited by the type of deposition, etching polishing,and patterning steps described herein. Nor is the invention limited toany specific type of semiconductor device. For example, the presentinvention may be implemented in a dynamic random access memory (DRAM)device or non volatile memory device. Other additions, subtractions, ormodifications are obvious in view of the present disclosure and areintended to fall within the scope of the appended claims.

What is claimed is:
 1. A method for manufacturing a semiconductor devicecomprising: forming first recesses over a semiconductor substrate;forming a first insulation film over the first recesses and thesemiconductor substrate; forming second recesses by etching the firstinsulation film and the semiconductor substrate; forming a secondinsulation film over the second recesses and the first insulation film;forming gate patterns over the second insulation film, wherein the gatepatterns each fill in the second recesses and extend upwards whilehaving a substantially uniform width; and forming a second insulationfilm pattern and a first insulation film pattern at a first edge and ata second edge of each of the gate patterns by etching the second and thefirst insulation films until the semiconductor substrate is exposed,wherein a sum of a thickness of the second and a thickness of the firstinsulation film patterns is different from each other at the first edgeand at the second edge .
 2. The method according to claim 1, wherein thefirst recesses are formed to have a depth of 100 Å˜400 Å.
 3. The methodaccording to claim 1, wherein the first insulation film includes anoxide film and is formed to have a thickness of 10 Å˜100 Å.
 4. Themethod according to claim 1, wherein the second recesses are formed tohave a depth of 1200 Å˜1500 Å.
 5. The method according to claim 1,wherein the second insulation film includes an oxide film and is formedto have a thickness of 10 Å˜100 Å.
 6. The method according to claim 1,wherein the width of the first recesses is greater than the width of thesecond recesses.
 7. The method according to claim 1, wherein thesemiconductor substrate coupled to a storage node contact plug is formedto be at a higher level than the semiconductor substrate coupled to abit line contact plug.
 8. The method according to claim 1, wherein theforming of the gate patterns includes: sequentially forming apolysilicon film, a metal silicide, and an oxide film over the secondinsulation film; and etching the polysilicon film, the metal silicide,and the oxide film using a gate pattern mask until the second insulationfilm is exposed.
 9. The method according to claim 1, after the formingof the gate patterns, the method further comprising: forming third andfourth insulation films over the gate patterns; and etching the thirdand fourth insulation films until the semiconductor substrate isexposed.
 10. A semiconductor device comprising: a gate pattern formedover a recess in a semiconductor substrate; and insulation film patternsformed over both edges of a lower part of the gate pattern, whereinthicknesses of the insulation film patterns formed over both edges ofthe gate pattern are different from each other.
 11. The semiconductordevice according to claim 10, wherein a thickness of the insulation filmpattern formed over the semiconductor substrate coupled to a storagenode contact plug is greater than a thickness of the insulation filmpattern formed over the semiconductor substrate coupled to a bit linecontact plug.
 12. The semiconductor device according to claim 11,wherein the semiconductor substrate coupled to the storage node contactplug is formed to be at a higher level than the semiconductor substratecoupled to the bit line contact plug.
 13. A semiconductor devicecomprising: a vertical gate provided in a substrate; first and secondjunction regions each coupled to the vertical gate; a first insulationfilm provided between the vertical gate and the first junction region;and a second insulation film provided between the vertical gate and thesecond junction region, wherein the first insulation film is thickerthan the second insulation film.
 14. The semiconductor device of claim13, wherein the first and the second junction regions have a stepdifference from each other.
 15. The semiconductor device of claim 13,wherein the substrate coupled to the first junction region has a stepdifference from the substrate coupled to the second junction region. 16.The semiconductor device of claim 13, wherein the first junction regionis configured to have a relatively higher potential of gate induceddrain leakage (GIDL) value than the second junction region.
 17. Thesemiconductor device of claim 13, wherein the first junction region iscoupled to a storage node and the second junction region is coupled to abit line.
 18. The semiconductor device of claim 13, wherein the verticalgate is a recess gate or a buried gate.
 19. The semiconductor device ofclaim 13, the device further comprising: a third insulation filmextending from the first insulation film upward along a first sidewallof the vertical gate, wherein the third insulation film is thinner thanthe first insulation film.
 20. The semiconductor device of claim 13, thedevice further comprising: a fourth insulation film extending from thesecond insulation film upward along a second sidewall of the verticalgate, wherein the fourth insulation film is formed to substantially thesame thickness as the second insulation film.